This study investigates whether macaques and humans possess
a common pattern of relative growth during the fetal period. The fetal populations
consist of 16 male pigtailed macaques (mean age 20.5 gestational weeks) and
17 humans (9 males and 8 females; mean age 29.5 gestational weeks). For
each individual, three-dimensional coordinates of 18 landmarks on the skull
were collected from three-dimensional computed tomographic (CT) reconstructed
images and two-dimensional CT axial slices. Early and late groups were created
from the human (early mean age 24 weeks, N=8; late mean age 34 weeks, N=9)
and macaque populations (early mean age 17.7 weeks, N=7; late mean age 23
weeks, N=9). Inter- and intraspecific comparisons were made between the early
and late groups. To determine if macaques and humans share a common fetal
pattern of relative growth, human change in shape estimated from a comparison
of early and late groups was compared to the pattern estimated between early
and late macaque groups. Euclidean Distance Matrix Analysis (EDMA) was used
in all comparisons. Intraspecific comparisons indicate that the growing
fetal skull displays the greatest amount of change along mediolateral dimensions.
Changes during human growth are primarily localized to the basicranium and
palate, while macaques experience localized change in the midface. Interspecific
comparisons indicate that the two primate species do not share a common pattern
of relative growth and the macaque pattern is characterized by increased
midfacial growth relative to humans. Our results suggest that morphological
differences in the craniofacial skeleton of these species are in part established
by differences in fetal growth patterns.

Images from this publication.

Landmarks digitized in this study.

Growth comparison between macaques and humans. Linear distances that display
significant confidence intervals are illustrated on 3D reconstructions of
lateral (A), midsagittal (B), and frontal views (C) of a fetal human skull.
Solid lines indicate linear distances that are significantly larger in the
macaque interval relative to the human interval. Dotted lines indicate linear
distances that are significantly smaller in the macaque interval relative
to the human interval.